Good for warming up your muscles and joints before your routine, getting your heart rate up and helping to improve your overall fitness level.
Also known as stretching, these exercises help relieve stiff joints and improve your range of motion. Muscles work best when they are at their optimum length, also improving mobility.
Muscles not only help you move they also act as shock absorbers. The stronger the muscles around the hip and knee, the beter the shock absorption and stability — meaning less strain (and pain) on the joint.